Research On Blasting Vibration Law And Amplifying Effect Of High Side Wall In Deep Cavern

With the continuous deepening of the development and utilization of underground space,a large number of upright side walls with shaft heights of hundreds of meters and high side walls of underground powerhouses with a height of nearly 100 meters have been successively constructed,and the difficulty of blasting excavation construction and vibration prediction control of the upright high side walls is increasing day by day.During the blasting and excavation process,more energy is propagated on the surface of the side wall in the form of vibration waves,which induces damage and destruction of the surrounding rock and lining,which in turn leads to the instability of the side wall and the failure of the sealing function,which greatly increases the construction safety.Risk and investment in operation and maintenance.Therefore,the vibration propagation law of the high side walls of deep burial chambers has become a technical problem.In this paper,with the background of blasting excavation of the Baihetan underground main powerhouse of a world-class hydropower station,the comprehensive analysis method was used to study the propagation attenuation law and amplification effect of the PPV propagation in the underground cavern high side wall from three aspects: theoretical model,field test and numerical simulation.In terms of the theoretical model,based on the simple supported plate and simple supported beam mechanical analysis model,the vibration response mechanism of the surrounding rock of the side wall of the underground cavern is analyzed,and the PPV dimensionless quantity considering the "boundary constraint" factor is obtained,combined with the dimension The analytical method obtains the PPV prediction formula for the surrounding rock of the side wall of the underground cave.In the field test,based on the blasting test of the side wall of the Taohuazui underground cave,the attenuation law of the side wall blasting PPV and the distribution characteristics of the amplification effect were analyzed,and it was confirmed that the simple-supported plate model and its PPV prediction formula under certain conditions High prediction accuracy.In terms of numerical simulation,the Ls-Dyna dynamic finite element software was used to model the Taohuazui underground cavern as a prototype.By analyzing the influence of the side wall length-to-height ratio,the magnitude of the ground stress and the lateral pressure coefficient on the underground cavern blasting PPV,a study was conducted The PPV attenuation law and the distribution characteristics of amplification effect of underground cavern blasting are revealed.Finally,the measured blasting data of Baihetan confirmed that the model and PPV prediction formula in this paper can describe the vibration propagation law of the high side wall of the deep burial cavity in a certain range.The main conclusions are as follows:(1)The blasting vibration velocity in all three directions shows an overall decreasing trend as the elevation difference increases;the peak vibration velocity of Y particle perpendicular to the side wall surface is the largest,which is larger than the peak vibration velocity of other two directions.(2)There is a vibration amplification effect in the high-side walls of deep underground caves,and the amplification factor shows a "central amplification" distribution.The reason for this analysis is that the explosion stress wave will be reflected when it reaches the side wall of the underground cave,and the reflected stress wave superimposed with the incident stress wave will aggravate the vibration effect of the side wall.(3)The blasting PPV of the side wall of the underground cave increases correspondingly with the increase of the aspect ratio of the side wall and the surrounding rock stress,but the increasing trend is not obvious;the blasting PPV of the side wall of the cave is basically not affected by the lateral pressure coefficient influences.